TextMeasurer.TryMeasureCharacterBounds doesn't return bounds for some characters using Style Script font

[Kizuto3]

I ran into a problem where TextMeasurer.TryMeasureCharacterBounds removes some glyphs when measuring a text using Style Script font. I am using the latest version of SixLabors.Fonts (2.0.3) with .NET 8 on Windows 10.

Steps to reproduce:

using SixLabors.Fonts;

var textContent = "Please enter the text";

var fontData = File.ReadAllBytes(@"<path to the font>\Style Script.ttf");

using var stream = new MemoryStream(fontData);

var fontsCollection = new FontCollection();
var fontFamily = fontsCollection.Add(stream);

var font = fontFamily.CreateFont(16f);

var renderOptions = new TextOptions(font)
{
    Dpi = 96,
    VerticalAlignment = VerticalAlignment.Top,
    HorizontalAlignment = HorizontalAlignment.Left,
    KerningMode = KerningMode.Auto
};

if (TextMeasurer.TryMeasureCharacterBounds(textContent.AsSpan(), renderOptions, out var bounds))
{
    Console.WriteLine($"Bounds length: {bounds.Length}");
    Console.WriteLine($"textContent length: {textContent.Length}");
}
else
{
    Console.WriteLine("Failed to measure bounds");
}

Console.ReadLine();

After some debugging I found that LookupType4SubTable.TrySubstitution removes the second 'e' from "enter" and 't' from "the". This looks like a bug, though I am not sure.
Here's a ttf file of a font I am using:
Style Script.zip

[JimBobSquarePants]

There's no issue here.

Here's what is happening:

• The glyphs at positions 10 and 11 e (507) and r (801) are replaced by ligature e_r (509).
• Following that substitution, the glyphs at position 12 and 13 t (851) h (588) are replaced by ligature t_h (852)

This leaves 19 glyphs in total instead of the original 21.

As you can see the output is correct.

If you wish to see a step by step demonstration of the process you can use this website.
https://www.corvelsoftware.co.uk/crowbar/